/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.druid.frame.channel;

import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import org.apache.druid.frame.Frame;

import java.util.NoSuchElementException;

/**
 * Empty channel.
 */
public class ReadableNilFrameChannel implements ReadableFrameChannel
{
  public static final ReadableNilFrameChannel INSTANCE = new ReadableNilFrameChannel();

  private ReadableNilFrameChannel()
  {
  }

  @Override
  public boolean isFinished()
  {
    return true;
  }

  @Override
  public boolean canRead()
  {
    return false;
  }

  @Override
  public Frame read()
  {
    throw new NoSuchElementException();
  }

  @Override
  public ListenableFuture<?> readabilityFuture()
  {
    return Futures.immediateFuture(null);
  }

  @Override
  public void close()
  {
    // Nothing to do.
  }
}
